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2009 - 2010 Flu Activity Report

While influenza is not a reportable disease in Illinois, the Illinois Department of Public Health examines reports from many health care sites throughout the state. These sites include physician offices, emergency departments and nursing homes that report acute illness, and schools that report absenteeism rates. Accordingly, the Department monitors disease trends and influenza activities as they occur on a weekly basis.

A detailed surveillance report for each week can be viewed by clicking on the desired week in the table below. This weekly surveillance report summarizes regional and state influenza data used to determine the weekly influenza activity level and national activity levels reported by state and territorial epidemiologists.

Year Week Beginning Week Ending Reported Influenza Activity
2010 May 23 May 29 No Activity
2010 May 16 May 22 Sporadic Activity
2010 May 9 May 15 Sporadic Activity
2010 May 2 May 8 Sporadic Activity
2010 April 25 May 1 Sporadic Activity
2010 April 18 April 24 Sporadic Activity
2010 April 11 April 17 Sporadic Activity
2010 April 4 April 10 Sporadic Activity
2010 March 28 April 3 Sporadic Activity
2010 March 21 March 27 Sporadic Activity
2010 March 14 March 20 Sporadic Activity
2010 March 7 March 13 Sporadic Activity
2010 February 28 March 6 Sporadic Activity
2010 February 21 February 27 Sporadic Activity
2010 February 14 February 20 Sporadic Activity
2010 February 7 February 13 Sporadic Activity
2010 January 31 February 6 Sporadic Activity
2010 January 24 January 30 Sporadic Activity
2010 January 17 January 23 Sporadic Activity
2010 January 10 January 16 Sporadic Activity
2010 January 3 January 9 Sporadic Activity
2009 December 27 January 2 Local Activity
2009 December 20 December 26 Local Activity
2009 December 13 December 19 Local Activity
2009 December 6 December 12 Regional Activity
2009 November 29 December 5 Regional Activity
2009 November 22 November 28 Regional Activity
2009 November 15 November 21 Widespread Activity
2009 November 8 November 14 Widespread Activity
2009 November 1 November 7 Widespread Activity
2009 October 25 October 31 Widespread Activity
2009 October 18 October 24 Widespread Activity
2009 October 11 October 17 Widespread Activity
2009 October 4 October 10 Widespread Activity
2009 September 20 October 3 Widespread Activity
2009 September 27 September 26 Widespread Activity
2009 September 13 September 19 Widespread Activity
2009 September 6 September 12 Widespread Activity
2009 August 30 September 5 Regional Activity

No Activity No lab confirmed cases †
Sporadic Activity Isolated lab-confirmed cases OR Lab confirmed outbreak in one institution ‡
Local Activity Recent (within the past 3 weeks) lab evidence of influenza in region with increased ILI* OR Recent (within the past 3 weeks) lab evidence of influenza in region with the outbreaks; virus activity is no greater than sporadic in other regions**
Regional Activity Increased ILI* in >2 but less than half of the regions AND recent (within the past 3 weeks) lab confirmed influenza in the affected regions. OR Institutional outbreaks (ILI or lab confirmed) in >2 and less than half of the regions AND recent lab confirmed influenza in the affected regions**. A region is defined as the regions States use for public health purposes.
Widespread Activity Increased ILI* and/or institutional outbreaks (ILI* or lab confirmed) in at least half of the regions** AND recent (within the past 3 weeks) lab confirmed influenza in the state.

*ILI activity can be assessed using a variety of data sources including sentinel providers, school/workplace absenteeism, and other syndromic surveillance systems that monitor influenza-like illness.
Lab confirmed case=case confirmed by rapid diagnostic test, antigen detection, culture, or PCR. Care should be given when relying on results of point of care rapid diagnostic test kits during times when influenza is not circulating widely. The sensitivity and specificity of these tests vary and the predicative value positive may be low outside the time of peak influenza activity. Therefore, a state may wish to obtain laboratory confirmation of influenza by testing methods other than point of care rapid tests for reporting the first laboratory confirmed case of influenza of the season.
Institution includes nursing home, hospital, prison, school, etc.
** Region: population under surveillance in a defined geographical subdivision of a state. A region could be comprised of 1 or more counties and would be based on each state's specific circumstances. Depending on the size of the state, the number of regions could range from 2 to approximately 12. The definition of regions would be left to the state but existing state health districts could be used in many states. Allowing states to define regions would avoid somewhat arbitrary county lines and allow states to make divisions that make sense based on geographic population clusters. Focusing on regions larger than counties would also improve the likelihood that data needed for estimating activity would be available.

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